WHO IT'S BEST FOR: Couples, especially ones who don't agree on firmness level. It's also great for those who aren't sure what firmness level they prefer and want the ability to change it at any time. Sleep Number's smart beds are some of the best you'll find. HOW IT PERFORMED IN OUR TESTS:✔️ Adjustable firmness: The smart mattress allows you to customize the firmness level of each side of the bed from 1 to 100. Sleep Number beds perform best on their bases, especially if you want one with adjustable positions, but you can pair this with an existing bed frame.